The invention disclosed herein relates to wireless networks. More specifically, the invention relates to calibrating the automatic gain control (“AGC”) of a receiver in a wireless device.
Wireless local area networks (“WLAN”) allow electronic devices, such as computers, to have network connectivity without the use of wires. Network connections may be established via, for example, radio signals. Connections with existing wired networks may be provided by a wireless access point (“AP”) having a wired Internet or Ethernet connection and radio communication circuitry capable of transmitting data to and receiving data from any compatible wireless device. The AP may provide Internet and/or network connectivity to such wireless devices (e.g., portable computers) called receiver stations (“STA”) by transmitting and receiving data via radio signals.
Data signals transmitted from an AP to a STA or from a STA to an AP may vary in quality and strength. For example, an AP and a STA situated in relatively close proximity may achieve a strong communication signal, whereas an AP and a STA with a relatively large physical distance therebetween may achieve a weak communication signal. Depending on the quality of the signal received, a STA or an AP may use an AGC to amplify the received signal to a magnitude and phase suitable for analog-to-digital conversion. The AGC may automatically adjust the amount of gain based on signal characteristics. For instance, a greater gain may be applied to a weak received signal whereas a lesser gain may be applied to a strong received signal. In this manner, the AGC can consistently provide an analog-to-digital converter (“ADC”) with received signals of similar or identical strength, regardless of the strength of the signals received. Such use of an AGC permits use of the full dynamic range of the ADC.
Regular calibration of the AGC may provide wireless communication systems with enhanced performance. That is, it may be desirable to determine how the signal gain varies for different settings of the AGC. Certain hardware may be implemented in a STA or an AP to accomplish AGC calibration; however, additional hardware may be unacceptable due to, among other things, an increase in production cost. Thus, a technique to calibrate the AGC without the use of additional hardware is desirable.